1. Field of the Invention
The present invention relates to a stereoscopic imaging apparatus, and more particularly, to a technique for forming subject images that have passed through different areas in a horizontal direction of an photographic optical system on image sensors, respectively, to acquire a left viewpoint image and a right viewpoint image.
2. Description of the Related Art
Known as this type of stereoscopic imaging apparatus has conventionally been one including an optical system illustrated in FIG. 18 (National Publication of International Patent Application No. 2009-527007).
The optical system is configured to pupil-split subject images that have passed through different areas in a horizontal direction of a main lens 1 and a relay lens 2 with a mirror 4 and form the pupil-split subject images on image sensors 7 and 8 via imaging lens 5 and 6, respectively.
FIG. 19 illustrates separated states of images formed on an image sensor depending on a difference between front-focus, in-focus (best focus), and back-focus. In FIG. 19, the mirror 4 illustrated in FIG. 18 is omitted to compare differences in separation depending on the focus.
Out of the pupil-split images, the images that are in focus are formed at the same position on the image sensor (match), as illustrated in a portion (B) of FIG. 19, while the images that are in front focus or in back focus are respectively formed at different positions on the image sensor (separate), as illustrated in portions (A) and (B) of FIG. 19.
Therefore, the subject images, which have been pupil-split in a horizontal direction, are respectively acquired via the image sensors 7 and 8 so that a left viewpoint image and a right viewpoint image (a 3D image), between which there is a parallax that differs depending on a subject distance, can be acquired.
Japanese Patent Application Laid-Open No. 2009-168995 discusses an imaging apparatus capable of acquiring a left viewpoint image and a right viewpoint image corresponding to subject images, which have been pupil-split in a horizontal direction, in a similar manner to the above and performing focus detection (detecting a defocus amount) for a substantially whole area of a photographing screen, and particularly discusses being able to adjust a stereoscopic effect by changing an F-number of a diaphragm in Paragraph [0047].
A parallax (a separation width) between the left viewpoint image and the right viewpoint image, which are captured by this type of stereoscopic imaging apparatus, differ depending on a subject distance if the left and right viewpoint images have the same focal length and the same F-number. Particularly in the case of close-up photographing, a parallax of a near subject is too large so that stereoscopic viewing becomes impossible. On the other hand, a parallax of a far subject is often small so that no stereoscopic effect is given.
Japanese Patent Application Laid-Open No. 2009-168995 discusses being able to adjust a stereoscopic effect by changing an F-number of a diaphragm and does not discuss controlling the diaphragm.